1. Field of the Invention
The present invention relates to an armature, a dynamo electric machine having the same and a manufacturing method of the armature.
2. Description of Related Art
In an armature, each of conductive wires (magnet wires) is wound around each corresponding one of teeth of an armature core to form a plurality of windings. When an electric power is supplied from a commutator to the windings, the armature is rotated. In a case where the windings are wound by a lap winding method for partially overlapping the circumferentially adjacent windings, particularly when a deviation of a center of mass of the armature from a rotational center of the armature is relatively large, the rotational balance of the armature is deteriorated to cause vibrations during the rotation of the armature. Therefore, after the winding process, a corrective material is applied to the armature to perform a plus correction, or a portion of the armature core is cut to perform a minus correction, so that the weight balance of the armature is adjusted to achieve the relatively good balance.
However, the separate step, such as the adding of the corrective material or the cutting of the portion of the armature core, is required. Also, the number of components is increased by the corrective material. Also, a dedicate device for limiting dispersion of the corrective material is required. Furthermore, a dedicate tool for cutting the armature core is required. Therefore, the above method is not desirable.
In view of the above disadvantages, Japanese Examined Patent Publication No. H07-34630B2 (corresponding to U.S. Pat. No. 5,251,833) teaches the armature, in which the number of turns of each corresponding winding is adjusted to achieve the relatively good weight balance. In this way, the step, which is performed after the winding process to correct the balance, can be eliminated.
However, when the number of turns of each corresponding winding is changed to achieve the relatively good weight balance of the armature, a magnetic unbalance occurs due to the difference in the number of turns of the winding from one winding to another winding. Therefore, the armature is vibrated during its rotation due to the magnetic unbalance. As a result, the above method of changing the number of turns of each corresponding winding is not advantageous.